The concept of boat trailers is well known. A boat trailer usually consists of an elongated metal frame with one or more sets of wheels positioned near approximately one end. The other end terminates in a tongue for mounting to a hitch of a powered vehicle. Sometimes the boat trailer by means of its tongue is mounted onto a hitch ball which is mounted on a manually operated small wheeled hand truck. If the boat and trailer is light enough the boat on the trailer may be annually pushed around into position. However if a 360.degree. circle is attempted it will be noted that the axis of rotation is vertical through the axle of the wheels of the boat trailer or between the two axles of the boat trailer when the boat trailer has tandem axles. In either event the boat trailer is not as maneuverable as one would wish, especially in small marine yards; plus a large portion of the trailer at the tongue must extend beyond the boat.
A good boat dolly should have a number of attributes. It should be extremely stable. It should not require picking up of a heavy tongue. It should be very maneuverable, preferably turning 360.degree. on itself. It should be easy to transfer a boat from a conventional boat trailer to the boat dolly and vice versa. It should be relatively inexpensive of construction. It should accommodate various sizes of boats.